Regulators are simple and cheap way to create 5v or 3.3v (or any desired voltage if it is made for it)
Often when you use a microcontrollers (i.e. arduino) or a wireless communication module (i.e. xbee, bluetooth), you need to supply exact voltage the device requires. This is an example of sewable 3.3v regulator and 9V battery pouch with sewable 3.3v regulator.

* There are many different kind of 3.3v regulators. You do not have to stick with this one in the example. Although, when you get different ones, make sure the pin configuration is fitting to the connection on the battery pouch. (you may need to make a modification on the pouch connection)

Tools:
soldering iron
plier

Step 1:
split and bend the 3.3 regulator’s legs. make a little loop at the end of each regulator’s legs using plier.

Now you can use the little loop on each leg to sew it on fabrics. You can make 9V battery pouch to integrate it.
When making the pouch, make sure to not to use conductive thread as connection. It has too high resistance and I had problem supplying enough current.